APU A/C Compressor Replacement?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by PE_T, Aug 10, 2019.

  1. PE_T

    PE_T Road Train Member

    I think I said before I was going to check the fuses, but I forgot about them. Good thing you mentioned it, and lilillill said the fuse number. Thanks!
     
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  3. lilillill

    lilillill Sarcasm... it's not just for breakfast

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    Now I wonder if a blown clutch fuse causes an ACS alarm? Let us know the outcome.
     
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  4. mhyn

    mhyn Road Train Member

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    +1 . @PE_Trans give us an update.
     
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  5. PE_T

    PE_T Road Train Member

    I think it will work now, but I need to go fetch a 7.5 medium size fuse. I have a 7.5, but it’s too small! I’ll probably get some more freon and redo a vacuum. They say to vacuum for like 45 min, but my vacuum pump manual says 10 min. Which one is correct?
     
  6. mhyn

    mhyn Road Train Member

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    20-30 min would be enough.
     
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  7. lilillill

    lilillill Sarcasm... it's not just for breakfast

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    If you already vacuumed it, just blow the charge off and put two fresh cans in.

    Technically speaking, vacuuming by time doesn't really tell you if all the moisture and air is gone from the system. A micron gauge is the only way to tell. But for diy purposes, 45 minutes will probably do the trick.

    PAG oil is extremely hygroscopic. When the system is left open for any length of time, it's sucking moisture out of the air. Moisture is bad juju for AC systems. It forms acids which eat up all the metal parts and deteriorate hoses.

    Air in a system is non-condensible and will raise head pressures (high side) and cause poor performance.
     
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  8. PE_T

    PE_T Road Train Member

    Should I drain the compressor oil too as it may have now been contaminated? I have some PAG-46 on me (8 oz). My compressor does not specify the PAG number to use. It just says 180cc. My old compressor says PAG-46 180cc.

    I was checking the other time for the meaning of cc, and apparently it’s just a measurement that converts to 6.09 oz.
     

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  9. PE_T

    PE_T Road Train Member

    UPDATE—

    I regret to inform that I succeeded once again! Hahaha. Yeah, it was just the fuse. I reused the PAG oil, and did a vacuum. I found some Thermo King instructions for the Tripac Evolution where they say to use the high side to add the freon. Then Koon Trucking instructional YouTube video also says to use the high side. Now I actually used the low side, and it worked. I do not have a Tripac Evolution, just the old Tripac version. The TK instructions also mention to partially charge the compressor with freon before starting the engine.

    The APU is running and cooling fine, but I think I have bubbles in the drier sight glass. What happens if I leave it like that?
     

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    Last edited: Aug 25, 2019
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  10. lilillill

    lilillill Sarcasm... it's not just for breakfast

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    r134 will have bubbles and is not a reliable method for charging. 24 oz is a full charge in that system.
     
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  11. lilillill

    lilillill Sarcasm... it's not just for breakfast

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    Charging from the high side can only be done with an AC machine capable of injecting the refrigerant into a static system.

    If you attempt to charge from the high side with the little cans and a running compressor... well I hope you don't need your hands for anything. It will blow up the can in your hand as soon as you open the manifold valve.
     
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